Broadcasting across columns

Recall that when broadcasting across columns, NumPy requires you to be explicit that it should broadcast a vertical array, and horizontal and vertical 1D arrays do not exist in NumPy. Instead, you must first create a 2D array to declare that you have vertical data. Then, NumPy creates a copy of this 2D vertical array for each column and applies the desired operation.

A Python list called monthly_growth_rate with len() of 12 is available. This list represents monthly year-over-year expected growth for the economy; your task is to use broadcasting to multiply this list by each column in the monthly_sales array. The monthly_sales array is loaded, along with numpy as np.

Convert monthly_growth_rate, currently a Python list, into a one-dimensional NumPy array called monthly_growth_1D.
Reshape monthly_growth_1D so that it is broadcastable column-wise across monthly_sales; call the new array monthly_growth_2D.
Using broadcasting, multiply each column in monthly_sales by monthly_growth_2D.

Exercise

Broadcasting across columns

Instructions